The present invention relates to controls of the chip and the length of such chip which is produced in a machining process of an iron material or an iron alloy material, and more particularly to an apparatus and a method which are based on the electromagnetic principle for use in controlling the machining chip and the length of such machining chip.
An iron material and an iron alloy material are widely used in making various mechanical components or the structures of a machinery by machining process, in view of the fact that both the iron material and the iron alloy material have an excellent mechanical property and an excellent machinability. With the exception of a cast iron chip which is broken into small pieces in the machining process, an iron chip or an iron alloy chip produced in the machining process is generally in the form of a long and unbroken piece. Such long and unbroken chip can get twisted easily with a cutting tools, work pieces and machine parts. The operatior is often annoyed by such incident, which also can bring about an interruption of machining and can affect adversely the overall efficiency of the machining operation. Moreover, such incident can be hazardous to the operator's safety and can cause damages to the cutting edge of the machining tool, the work piece, and even the machinery. The long and unbroken piece of the machining chip has a high bulk ratio and is therefore difficult to be disposed of economically. The machining process has become automated and robotized, with the emphasis placed on a high metal removal rate. Such modern machining process is by no means free from the operational problems decribed above, as long as the problem of the long and unbroken pieces of the machining chip persists.
The prior art method of breaking apart the long machining chip comprises a lathe tool having a means capable of breaking apart the chip. As shown in FIG. 1, there are two kinds of such lathe tool. The FIGS. 1A and 1B show the groove type while the FIGS. 1C and 1D show the obstruction type. The surface of the lathe tool is provided with the groove or the obstruction piece located at an appropriate position presumed to be on the machining path. In addition, the machining conditions are selected in conformity with the shape of the chip breaking apparatus. For example, the machining depth, the machining speed, and the state in which the chip is under a high bending stress to reach a critical chip breaking curvature diameter at such time when the chip passes against the surface of the lathe tool are all taken into consideration so as to achieve an effective control of the chip breaking process. An alternative method is to guide the machining chip to smash into the machining transient surface S1 or into the belly surface S2 of the lathe tool so as to cause the chip to tear apart, as shown in FIGS. 2A and 2B.
There are many factors that affect the breakage of the machining chip. Such factors include the geometric shape of the cutting tool, the machining conditions such as the machining depth, the feed amount of the machining tool, the machining speed and so forth, the material quality of the work piece, and the circumstances under which the machining process takes place, such as the way that the chip wafts, the divergence of directions in which the chip twists, and the extent of the bending stress exerting on the chip upon being twisted. According to the chip breaking apparatus of the prior art, the surface of the cutting tool is provided at an appropriate location thereof with a groove or an obstruction piece of an appropriate shape so as to set up the geometric shape of the surface of the cutting tool and to select the machining conditions under which the chip breaking apparatus is used suitably to maximize the chip breaking effect. However, such prior art method is limited in design in that it fails to control effectively the all possible factors that affect the chip breaking operation, and that the geometric shape of the surface of the cutting tool is so fixed that it can not be changed in accordance with the changing conditions and circumstances of the machining process. In other words, the prior art method of the chip breaking is so limited that the machining tool is permitted to have only one kind of the geometric shape and that the effect of the chip breaking action is greatly undermined.